Positive electrode material and preparation method and usage thereof

ABSTRACT

This disclosure relates to the electrochemical field, and in particular, to a positive electrode material and a preparation method and usage thereof. The positive electrode material of this disclosure includes a substrate, where a general formula of the substrate is Li x Ni y Co z M k Me p O r A m , where 0.95≤x≤1.05, 0.5≤y≤1, 0≤z≤1, 0≤k≤1, 0≤p≤0.1, 1≤r≤5.2, 0≤m≤2, m+r≤2, M is selected from one or more of Mn and Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb, and A is selected from one or more of N, F, S, and Cl; and an oxygen defect level of the positive electrode material satisfies at least one of condition (1) or condition (2): (1) 1.77≤OD1≤1.90; or (2) 0.69≤OD2≤0.74.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/CN2020/084339 filed on Apr. 11, 2020, which claims priority tothe Chinese Patent Application No. 201910578163.0, filed on Jun. 28,which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to the electrochemical field, and in particular,to a long-life positive electrode material and a preparation method andusage thereof.

BACKGROUND

With escalation of energy crisis and environmental issues, developmentof new-type green energy sources becomes extremely urgent. Lithium-ionbatteries have been applied to various fields due to advantages such asa high specific energy, application in a wide range of temperature, alow self-discharge rate, a long cycle life, good safety performance, andno pollution. The lithium-ion batteries acting as a vehicle energysystem to replace conventional diesel locomotives have been graduallyput into trial around the world. However, lithium iron phosphate(LiFePO₄) and low nickel ternary (LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂) commonlyused at present are limited by nature of the material itself and cannotfully meet energy density requirements of traction batteries on apositive electrode material of lithium-ion batteries. Increasing nickelcontent in a high nickel ternary positive electrode material can improvethe energy density of batteries. Therefore, the high nickel ternarypositive electrode material is one of main objects of research ontraction batteries. However, with the increase of the nickel content,Li/Ni mixing of the positive electrode material has increasedsignificantly, and oxygen defects of the material have also increasedsignificantly. Cycle performance of high-capacity traction batteriesdeteriorates rapidly with a short calendar life, which is currently oneof bottlenecks of commercial mass production.

At present, main means for improving cycle performance in terms ofternary positive electrode material are optimizing main element content,doping, and modification by coating. With the three means, the cycleperformance can be improved to some extent, but still has a gap to meetthe market demand.

SUMMARY

In view of the disadvantages of the prior art, this disclosure isintended to provide a long-life positive electrode material and apreparation method and usage thereof to solve the problems in the priorart.

In order to achieve the above and other related purposes, one aspect ofthis disclosure provides a long-life positive electrode material,including a substrate, where the general formula of the substrate isLi_(x)Ni_(y)Co_(z)M_(k)Me_(p)O_(r)A_(m), where 0.95≤x≤1.05, 0.5≤y≤1,0≤z≤1, 0≤k≤1, 0≤p≤0.1, 1≤r≤5.2, 0≤m≤2, m+r≤2, M is selected from Mnand/or Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V,Ti, Sr, Sb, Y, W, and Nb, and A is selected from one or more of N, F, S,and Cl; and an oxygen defect level of the positive electrode materialsatisfies at least one of condition (1) or condition (2):

(1) 1.77≤OD1≤1.90, where OD1=(I₁₀₁/I₀₁₂)^(0.5), I₁₀₁ represents XRDdiffraction peak intensity of the (101) crystal plane of the positiveelectrode material in an XRD pattern, and I₀₁₂ represents diffractionpeak intensity of the (012) crystal plane of the positive electrodematerial in the XRD pattern; and

(2) 0.69≤OD2≤0.74, where OD2=(I₁₀₁/I₁₀₄)^(0.5), I₁₀₁ represents XRDdiffraction peak intensity of the (101) crystal plane of the positiveelectrode material in the XRD pattern, and I₁₀₄ represents diffractionpeak intensity of the (104) crystal plane of the positive electrodematerial in the XRD pattern.

Another aspect of this disclosure provides a positive electrode plate,including a positive electrode current collector and a positiveelectrode active material layer, where the positive electrode activematerial layer includes the positive electrode material.

Another aspect of this disclosure provides an electrochemical energystorage apparatus, including the positive electrode material or thepositive electrode plate.

Compared with the prior art, this disclosure has the followingbeneficial effects:

In this disclosure, the positive electrode material has a higher Nicontent, and fewer oxygen defects, so its crystal structure is stablewith a low Li/Ni mixing ratio, ensuring that a battery using thepositive electrode material has higher energy density and long cyclelife, and effectively suppressing gas generation during cycling.

DESCRIPTION OF EMBODIMENTS

A positive electrode material of this disclosure, a lithium-ion batteryincluding the positive electrode material, and a preparation methodthereof are described in detail below.

A first aspect of this disclosure provides a positive electrodematerial, including a substrate, where the general formula of thesubstrate is Li_(x)Ni_(y)CO_(z)M_(k)Me_(p)O_(r)A_(m), where 0.95≤x≤1.05,0.5≤y≤1, 0≤z≤1, 0≤k≤1, 0≤p≤0.1, 1≤r≤5.2, 0≤m≤2, m+r≤2, M is selectedfrom Mn and/or Al, Me is selected from one or more of Zr, Zn, Cu, Cr,Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb, and A is selected from one or moreof N, F, S, and Cl; and

an oxygen defect level of the positive electrode material satisfies atleast one of condition (1) and condition (2):

(1) 1.77≤OD1≤1.90, where OD1=(I₁₀₁/I₀₁₂)^(0.5), I₁₀₁ represents XRDdiffraction peak intensity of the (101) crystal plane of the positiveelectrode material in an XRD pattern, and I₀₁₂ represents diffractionpeak intensity of the (012) crystal plane of the positive electrodematerial in the XRD pattern; and

(2) 0.69≤OD2≤0.74, where OD2=(I₁₀₁/I₁₀₄)^(0.5), I₁₀₁ represents XRDdiffraction peak intensity of the (101) crystal plane of the positiveelectrode material in the XRD pattern, and I₁₀₄ represents diffractionpeak intensity of the (104) crystal plane of the positive electrodematerial in the XRD pattern.

A high nickel ternary material is prone to oxygen defects (LiMeO_(2-x))during sintering, while the relative level of oxygen defects is closelyrelated to structural stability and high-temperature storage performanceof the positive electrode material. Researchers of this application havefound that values of the oxygen defect levels OD1 and/or OD2 mainlydepend on process control related to oxygen binding such as a precursorpreparation process and a powder sintering process. By adjusting speed,temperature and pH of a stirring process during synthesis of theprecursor to improve adhesion ability of hydroxide ions, and adjustingsintering temperature, sintering time and oxygen flow of a sinteringprocess, the oxygen defect level of the positive electrode material canbe controlled to satisfy 1.77≤OD1≤1.90 and/or 0.69≤OD2≤0.74, which canensure that the high nickel positive electrode material has a relativelycomplete crystal structure and good structural stability. Therefore, thecrystal is less likely to collapse during intercalation anddeintercalation of lithium ions, which is beneficial to prolong servicelife.

In an embodiment of this disclosure, the oxygen defect level of thepositive electrode material is calculated by analyzing the diffractionpeak intensities of (003), (101), and (012) crystal planes by using theXRD pattern. The specific test conditions for the XRD pattern should beknown to those skilled in the art. For example, the test conditions forthe XRD pattern of the positive electrode material can be 1.6 kW power,a 1°/min test step size, and a deduction of kα2 from the test pattern.The inventors have diligently studied and found that the oxygen defectlevel of the positive electrode material is closely related to thestability of the crystal structure, which can be characterized bycharacterizing a relationship between diffraction peak intensity ofspecial crystal planes in the XRD pattern. According to a characteristicof an R-3m point group structure of a ternary layered material, thecrystal planes with no contribution from oxygen atoms and moderateintensity include (003) and (101), the crystal planes with positivecontribution from oxygen atoms and moderate intensity include (104) and(110), and crystal planes with negative contribution from oxygen atomsand moderate intensity include (012). Therefore, the oxygen defect levelof the ternary layered material characterized by I₁₀₁/I₀₁₂ or I₁₀₁/I₁₀₄has higher accuracy. Further, a relationship between the intensity ratioof the XRD diffraction peaks, I₁₀₁/I₀₁₂ or I₁₀₁/I_(104,) and x istypically a cubic polynomial function, while a relationship between anintensity ratio with power-of-0.5 and x is typically a linear function.Therefore, the intensity ratio with power-of-0.5 is an indicator ofoxygen defects. Since I₀₁₂ has small peak intensity,OD1=(I₁₀₁/I₀₁₂)^(0.5) has a large variation range and is highlyrecognizable, which is suitable to serve as a main indicator of oxygendefects. According to the calculation function, it can be learned thatthe larger (I₁₀₁/I₀₁₂)^(0.5) indicates a smaller x value in themolecular formula LiMeO_(2-x) and fewer oxygen defects in the material,and vice versa. In addition, I₁₀₁ and I₁₀₄ have obvious intensity andmoderate half-peak width, also suitable to serve as main indicators ofoxygen defects.

In the positive electrode material provided in an embodiment of thisdisclosure, the OD1 may range from 1.77 to 1.90, 1.77 to 1.78, 1.78 to1.79, 1.79 to 1.80, 1.80 to 1.81, 1.81 to 1.82, 1.82 to 1.83, 1.83 to1.84, 1.84 to 1.85, 1.85 to 1.86, 1.86 to 1.87, 1.87 to 1.88, 1.88 to1.89, or 1.89 to 1.90. The OD2 may range from 0.69 to 0.74, 0.69 to0.70, 0.70 to 0.71, 0.71 to 0.72, 0.72 to 0.73, or 0.73 to 0.74.

In the positive electrode material provided by an embodiment of thisdisclosure, when the oxygen defect level of the positive electrodematerial satisfies both conditions of 1.77≤OD1≤1.90 and 0.69≤OD2≤0.74,the oxygen defect level in the crystal structure of a layered ternarypositive electrode material can be more accurately characterized, makingthe characterization of oxygen defects more reliable. In addition, thelayered ternary material that meets the above conditions has a highlystable crystal structure, so it is not prone to have gassing issue underhigh temperature storage conditions and has a longer cycle life.

In the positive electrode material provided by an embodiment of thisdisclosure, when the positive electrode material is single-crystal orsingle-crystal-like particles, an OD1 value of the material is typicallysmaller than an OD1 value of the material when the positive electrodematerial is secondary particles. The reason is that single-crystal orsingle-crystal-like particles are synthesized at higher sinteringtemperature, which is more likely to produce oxygen defects. Therefore,the relative amount of oxygen defects in a single-crystal ternarymaterial needs to be controlled to be even lower. For example, when thepositive electrode material is single-crystal or single-crystal-likeparticles, OD1 can range from 1.77 to 1.87; and for another example,when the positive electrode material is secondary particles, OD1 canrange from 1.82 to 1.90. For another example, when the positiveelectrode material is single-crystal or single-crystal-like particles,OD2 can range from 0.69 to 0.71; and for another example, when thepositive electrode material is secondary particles, OD2 can range from0.71 to 0.74.

In the positive electrode material provided by an embodiment of thisdisclosure, a Li/Ni mixing ratio of the positive electrode material maybe 0.1% to 3%, and preferably, the Li/Ni mixing ratio of the positiveelectrode material may be 0.5% to 2%. The Li/Ni mixing ratio cantypically be calculated by collecting percentages of Ni atoms and Liatoms in a lithium layer and a transition metal layer through refiningXRD data. Generally speaking, there is no fixed absolute mixing ratio oflithium and nickel. A larger value does not necessarily mean poorerperformance, and a material with a higher mixing ratio may sometimesinclude a protective layer that can inhibit side reactions at aninterface. In an embodiment of this disclosure, the Li\Ni mixing ratioof the positive electrode material being in the above range can reduceimpact on active lithium participating in intercalation/deintercalationreaction, allowing less impact on gram capacity of the ternary positiveelectrode material, and ensuring an insignificant increase in DCR duringcycling.

In the positive electrode material provided by an embodiment of thisdisclosure, a mean microstress (Mean Microstress, MMS) of the positiveelectrode material may be in a range of 0.03 to 0.20, 0.03 to 0.04, 0.04to 0.05, 0.05 to 0.06, 0.06 to 0.07, 0.07 to 0.08, 0.08 to 0.09, 0.09 to0.10, 0.10 to 0.12, 0.12 to 0.14, 0.14 to 0.16, 0.16 to 0.18, or 0.18 to0.20. When the mean microstress MMS of the positive electrode materialis within the above range, the crystal structure of the positiveelectrode material is relatively stable and the internal structure ofpowder particles is relatively compact. Therefore, the powder particlesare not prone to break during charging and discharging withintercalation/deintercalation of lithium ions, which is conducive tofurther improving the cycle life and alleviating the gassing issue oflithium-ion batteries. In this disclosure, the mean microstressMMS=(β_(hkl)·cot θ_(hkl))/4, where β_(hkl) represents a half-peak widthof a characteristic diffraction peak (hkl) in the XRD pattern of thepositive electrode material, and θ_(hkl) represents a diffraction anglecorresponding to the characteristic diffraction peak (hkl) in the XRDpattern of the positive electrode material. When the positive electrodematerial is single-crystal or single-crystal-like particles, MMS may bein a range of 0.03 to 0.07, 0.03 to 0.04, 0.04 to 0.05, 0.05 to 0.06, or0.06 to 0.07. When the positive material is secondary particles, MMS maybe in a range of 0.07 to 0.20, 0.07 to 0.08, 0.08 to 0.09, 0.09 to 0.10,0.10 to 0.12, 0.12 to 0.14, 0.14 to 0.16, 0.16 to 0.18, or 0.18 to 0.20.In this disclosure, the MMS can be tested in accordance with the methodgiven in the examples. Such testing method focuses on ensuring a stableXRD baseline for the tested sample, and the least possible fluctuationof half-peak width values of diffraction peaks, so as to ensurereliability of the MMS data.

In the positive electrode material provided by an embodiment of thisdisclosure, the substrate internally may contain a doping element, wherethe doping element is selected from one or more of Mg, Al, Ti, Co, Fe,Cd, Zr, Mo, Zn, B, P, Cu, V, and Ag. Preferably, the doping element maybe selected from one or more of Al, Ti, and Zr, and is electrochemicallyinert without changing its chemical valence state duringintercalation/deintercalation of lithium ions. In addition, as thedoping element has a slightly smaller the ionic radius than Ni, Co, andMn, the doping element can be better intercalated into a body center ofthe close-packed crystal structure, so that the crystal structure of thepositive electrode material is more stable, which is conducive toreducing the oxygen defect level of the positive electrode material. Inthe embodiments of this disclosure, a mass percentage of the dopingelement in the positive electrode material may be 200 ppm to 9000 ppm,200 ppm to 300 ppm, 300 ppm to 500 ppm, 500 ppm to 1000 ppm, 1000 ppm to2000 ppm, 2000 ppm to 3000 ppm, 3000 ppm to 5000 ppm, 5000 ppm to 7000ppm, or 7000 ppm to 9000 ppm. In the embodiments of this disclosure,doping the substrate with the foregoing element and controlling theamount of doping element to be within a specified range can increasebinding energy of Ni, Co, and Mn elements with oxygen in transitionmetal sites of the crystal structure, which is conducive to preparingternary cathode materials with fewer oxygen defects, and improvingstability and thermodynamic performance of the crystal structure. Italso ensures a higher intrinsic electronic conductivity of the positiveelectrode material, which is conducive to improving cycle performance.

In the positive electrode material provided by an embodiment of thisdisclosure, the substrate of the positive electrode material may includesecondary particles formed by agglomeration of primary particles, whereD_(v)50 of the secondary particles may be 5 μm to 18 μm, and a particlesize of the primary particles can be in a range of 0.1 μm to 1 μm. TheD_(v)50 typically refers to a particle size of the sample with acumulative volume distribution percentage reaching 50%. Specifically,the D_(v)50 of the secondary particles may be 5 μm to 18 μm, 5 μm to 16μm, or 8 μm to 15 μm; and the particle size the primary particles may bein a range of 0.1 μm to 1 μm, 0.1 μm to 0.9 μm, 0.2 μm to 0.8 μm, or 0.2μm to 0.5 μm.

In the positive electrode material provided by an embodiment of thisdisclosure, the substrate of the positive electrode material may includesingle-crystal or single-crystal-like particles, where D_(v)50 of thesingle-crystal or single-crystal-like particles may be 1 μm to 7 μm, 1μm to 3 μm, 3 μm to 5 μm, or 5 μm to 7 μm, D_(v)10 may be 1 μm to 3 μm,and D_(v)90 may be 5 μm to 10 μm, 5 μm to 8 μm, or 8 μm to 10 μm.Preferably, D_(v)50 of the single-crystal particles is 3 μm to 5 μm.

In the positive electrode material provided by an embodiment of thisdisclosure, the positive electrode material may further include acoating layer located on a surface of the substrate, where the coatinglayer includes a coating element, and the coating element is selectedfrom one or more of Al, Ba, Zn, Ti, W, Y, Si, Sn, and B. Providing acoating layer on the surface of the substrate can effectively passivatethe surface of the high nickel lithium transition metal oxide, thusisolating it from an electrolytic solution, reducing the amount ofresidual lithium on the surface of the active material, and alleviatingthe gassing issue. If the oxide used is a simple oxide with excellention conductivity and relatively poor electronic conductivity,polarization of the positive electrode material may be increased andcycle performance of the battery may be deteriorated. Therefore, in theembodiments of this disclosure, in combination with modification bycoating the surface of the substrate with an oxide, a specified dopingelement is used with an optimized doping amount, allowing higherintrinsic electronic conductivity of the positive electrode material,and less residual lithium and other impurities on the surface. Thiseffectively reduces side reactions of the material with the electrolyticsolution, and reduces interface resistance between the electrolyticsolution and the positive electrode active material, thereby greatlyreducing the polarization of the battery and improving the cycleperformance and rate performance of the battery.

In a preferred embodiment of this disclosure, the coating elementcontent in the coating layer ranges from 100 ppm to 3000 ppm, morepreferably, 200 ppm to 2000 ppm, and the coating layer typically refersto a material covering the surface of a positive electrode particlewithin thickness of 5 nm to 20 nm.

In the positive electrode material provided by an embodiment of thisdisclosure, the positive electrode material typically has some powderresistivity. For example, the powder resistivity ρ of the positiveelectrode material under 12 MPa may be 10 Ω·cm to 4500 Ω·cm, preferably,1000 Ω·cm to 4000 Ω·cm, more preferably, 1000 Ω·cm to 2000 Ω·cm. In anembodiment of this disclosure, in order to obtain a low oxygen defectlevel, the high nickel ternary positive electrode material needs adoping and/or coating process. This may lead to a high powderresistivity of the positive electrode material and deteriorate kineticsof the battery as the doping element and the coating layer arechemically inert elements. In an embodiment of this disclosure, thedoping and/or coating amount and the synthesis process are adjusted tofurther control the powder resistivity of the positive electrodematerial to be within the above range, thus making a relatively highintrinsic electronic conductivity of the positive electrode material andreducing the interface resistance between the electrolytic solution andthe positive electrode active material. In turn, polarization of thebattery is greatly reduced and cycle performance and service life of thebattery are further improved.

In some embodiments of this disclosure, the powder resistivity ρ of thepositive electrode material under 12 MPa may be in a range of 10 Ω·cm to4500 Ω·cm, 10 Ω·cm to 4000 Ω·cm, 10 Ω·cm to 3000 Ω·cm, 10 Ω·cm to 2000Ω·cm, 1000 Ω·cm to 2000 Ω·cm, 2000 Ω·cm to 3000 Ω·cm, or 3000 Ω·cm to5000 Ω·cm.

In an embodiment of this disclosure, the powder resistivity of thepositive electrode active material under 12 MPa can be measured by aknown powder resistivity test method. In a specific embodiment of thisdisclosure, a four-probe method can be used to test the powderresistivity of the positive electrode active material under 12 MPa. Thetest method includes: adding 0.4 g of positive electrode active materialpowder to a sample mold (with an inner diameter of 11.28 mm), applying12 MPa pressing force to the powder through a press machine, and readingthe powder resistivity of the positive electrode active material under12 MPa through a resistivity meter after the pressure is stabilized.

In the positive electrode material provided by an embodiment of thisdisclosure, Li₂CO₃ content in the residual lithium on the surface of thepositive electrode material (that is, a mass of Li₂CO₃ in the residuallithium on the surface of the substrate relative to a total mass of thepositive electrode material) is less than 3000 ppm, and preferably,Li₂CO₃ content in the residual lithium is less than 2000 ppm. LiOHcontent in the residual lithium on the surface of the positive electrodematerial (that is, a mass of LiOH in the residual lithium on the surfaceof the positive electrode material relative to the total mass of thepositive electrode material) is less than 5000 ppm, and preferably, LiOHcontent in the residual lithium is less than 4000 ppm. The substrate ofthe positive electrode material in an embodiment of this disclosure islithium nickel cobalt manganese oxide with high nickel content, and thesurface residual lithium content is usually high. Providing the coatinglayer on the surface of the substrate can effectively reduce theresidual lithium content on the surface, but may lead to greaterpolarization of the positive electrode material. Choosing a positiveelectrode material with a surface residual lithium content in the aboverange can strike an effective balance between gassing and polarizationproblems, helping to obtain a battery with higher capacity,insignificant gassing, and excellent cycle and rate performance.

A second aspect of this disclosure provides a method for preparing thepositive electrode material, including: mixing and sintering rawmaterials of a substrate to provide the substrate. Those skilled in theart can control the oxygen defect level in a ternary material byadjusting processes related to oxygen binding such as a precursorpreparation process and a powder sintering process. Specifically, thepositive electrode material in the first aspect of this disclosure isprovided by adjusting speed, temperature, and pH of a stirring processduring precursor synthesis and adjusting sintering temperature,sintering time, and oxygen flow during sintering. The raw materialsrequired to prepare the substrate should be known to those skilled inthe art. For example, the raw materials of the substrate may include aternary material precursor of nickel-cobalt-manganese and/or aluminum, alithium source, an M source, a Me source, an A source, and the like, andproportions of the raw materials are typically based on proportions ofthe elements in the substrate. More specifically, the ternary materialprecursor may include, but is not limited to,Ni_(0.5)Co_(0.2)Mn_(0.3)(OH)₂, Ni_(0.5)Co_(0.25)Mn_(0.25)(OH)₂,Ni_(0.55)Co_(0.15)Mn_(0.3)(OH)₂, Ni_(0.55)Co_(0.1)Mn_(0.35)(OH)₂,Ni_(0.55)Co_(0.05)Mn_(0.4)(OH)₂, Ni_(0.6)Co_(0.2)Mn_(0.2)(OH)₂,Ni_(0.75)Co_(0.1)Mn_(0.15)(OH)₂, Ni_(0.8)Co_(0.1)Mn_(0.1)(OH)₂,Ni_(0.88)Co_(0.05)Mn_(0.07)(OH)₂, 0.9Ni_(0.8)Co_(0.2)(OH)₂.0.1Al₂(OH)₃,or 0.9Ni_(0.9)Co_(0.05)Mn_(0.05)(OH)₂.0.1Al₂(OH)₃; the lithium sourcemay be a lithium-containing compound, where the lithium-containingcompound may include but is not limited to one or more of LiOH.H₂O,LiOH, Li₂CO₃, Li₂O, and the like; the Me source may typically be acompound containing Me element, where the compound containing Me elementmay be one or more of an oxide, a nitrate, a carbonate containing atleast one element of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, orAl; and the A source may be a compound containing element A, where thecompound containing element A may include but is not limited to one ormore of LiF, NaCl, or NaBr. For another example, a secondary particlewith an OD1 value ranging from 1.79 to 1.90 can be prepared at asintering temperature of 780° C. to 900° C., 780° C. to 800° C., 800° C.to 820° C., 820° C. to 840° C., 840° C. to 860° C., 860° C. to 880° C.,or 880° C. to 900° C., with a sintering time of 5 h to 15 h, 5 h to 7 h,7 h to 9 h, 9 h to 11 h, 11 h to 13 h, or 13 h to 15 h, and an oxygenconcentration of 20% to 35%, 20% to 25%, 25% to 30%, or 30% to 35%. Foranother example, a single-crystal or single-crystal-like particle withan OD1 value ranging from 1.77 to 1.87 can be prepared at a sinteringtemperature of 850° C. to 950° C., 850° C. to 870° C., 870° C. to 890°C., 890° C. to 910° C., 910° C. to 930° C., or 930° C. to 950° C., witha sintering time of 5 h to 15 h, 5 h to 7 h, 7 h to 9 h, 9 h to 11 h, 11h to 13 h, or 13 h to 15 h, and an oxygen concentration of 20% to 40%,20% to 25%, 25% to 30%, 30% to 35%, or 35% to 40%. For another example,a secondary particle with an OD2 value ranging from 0.70 to 0.74 can beprepared at a sintering temperature of 780° C. to 900° C., 780° C. to800° C., 800° C. to 820° C., 820° C. to 840° C., 840° C. to 860° C.,860° C. to 880° C., or 880° C. to 900° C., with a sintering time of 5 hto 15 h, 5 h to 7 h, 7 h to 9 h, 9 h to 11 h, 11 h to 13 h, or 13 h to15 h, and an oxygen concentration of 20% to 35%, 20% to 25%, 25% to 30%,or 30% to 35%. For another example, a single-crystal orsingle-crystal-like particle with an OD2 value ranging from 0.69 to 0.72can be prepared at a sintering temperature of 850° C. to 950° C., 850°C. to 870° C., 870° C. to 890° C., 890° C. to 910° C., 910° C. to 930°C., or 930° C. to 950° C., with a sintering time of 5 h to 15 h, 5 h to7 h, 7 h to 9 h, 9 h to 11 h, 11 h to 13 h, or 13 h to 15 h, and anoxygen concentration of 20% to 40%, 20% to 25%, 25% to 30%, 30% to 35%,or 35% to 40%.

In the preparation method of the positive electrode material provided inan embodiment of this disclosure, when the substrate is provided with acoating layer on the surface, the preparation method may furtherinclude: forming the coating layer on the surface of the substrate. Themethod of forming the coating layer on the surface of the substrateshould be known to those skilled in the art, and for example, mayinclude: sintering the substrate under a condition with presence of acompound containing a coating element, so as to form the coating layeron the surface of the substrate. Based on parameters such as compositionof the coating layer and the powder resistivity of the substrate, thoseskilled in the art can select a proper type, proportion, and sinteringcondition for the compound containing the coating element.

For example, the compound containing the coating element may include butis not limited to one or more of Al₂O₃, ZnO, ZrO₂, TiO₂, MgO, WO₃, Y₂O₃,Co₂O₃, Ba(NO₃)₂, Co₂O₃, P₂O₅, or H₃BO₃. For another example, the amountof the coating element used may be 0.01 wt % to 0.5 wt %, 0.01 wt % to0.05 wt %, 0.05 wt % to 0.1 wt %, 0.1 wt % to 0.2 wt %, 0.2 wt % to 0.3wt %, 0.3 wt % to 0.4 wt %, or 0.4 wt % to 0.5 wt % of a mass of thesubstrate. For another example, the sintering temperature may be 300° C.to 650° C., 300° C. to 350° C., 350° C. to 400° C., 400° C. to 450° C.,450° C. to 500° C., 500° C. to 550° C., 550° C. to 600° C., or 600° C.to 650° C., the sintering time may be 2 h to 5 h, 2 h to 3 h, 3 h to 4h, or 4 h to 5 h, and the oxygen concentration may be 20% to 30%, 20% to22%, 22% to 24%, 24% to 26%, 26% to 28%, or 28% to 30%.

A third aspect of this disclosure provides a positive electrode plate,where the positive electrode plate includes a positive electrode currentcollector and a positive electrode active material layer, and thepositive electrode active material layer includes the positive electrodematerial in the first aspect of this disclosure. The positive electrodecurrent collector may typically be a layer, and the positive electrodeactive material layer may typically cover at least partially the surfaceof the positive electrode current collector, or may be a layer extendingalong the surface of the positive electrode current collector. Thepositive electrode current collector is typically a structure or a partthat collects current, for example, a metal foil (for example, a copperfoil or an aluminum foil). Those skilled in the art may select asuitable method for preparing the positive electrode plate. For example,the following steps may be included: mixing the positive electrodematerial, a binder, and a conductive agent to form a slurry, andapplying the slurry on the positive electrode current collector.

A fourth aspect of this disclosure provides an electrochemical energystorage apparatus, including the positive electrode material in thefirst aspect of this disclosure or the positive electrode plate in thethird aspect of this disclosure. The electrochemical energy storageapparatus may be a super capacitor, a lithium-ion battery, a lithiummetal battery, or a sodium-ion battery. In the embodiments of thisdisclosure, only an embodiment in which the electrochemical energystorage apparatus is a lithium-ion battery is illustrated, but thisdisclosure is not limited thereto.

The lithium-ion battery provided by the embodiments of this disclosuremay typically include a positive electrode plate, a negative electrodeplate, a separator sandwiched between the positive electrode plate andthe negative electrode plate, and an electrolytic solution. The methodfor preparing the lithium-ion battery should be known to those skilledin the art. For example, the positive electrode plate, the separator,and the negative electrode plate may each be a layer, and may be cut toa target size and then stacked in order. The stack may be further woundto a target size to form a battery core, which may be further combinedwith the electrolytic solution to form a lithium-ion battery.

In the lithium-ion battery provided by the embodiments of thisdisclosure, the negative electrode plate typically includes a negativeelectrode current collector and a negative electrode active materiallayer located on a surface of the negative electrode current collector,and the negative electrode active material layer typically includes anegative electrode active material. The negative electrode activematerial may be various materials suitable for use as the negativeelectrode active material of a lithium-ion battery in the art, forexample, may include but is not limited to one or more of graphite, softcarbon, hard carbon, carbon fiber, mesophase carbon microbeads,silicon-based material, tin-based material, lithium titanate, or othermetals capable of forming alloys with lithium. The graphite may beselected from one or more of artificial graphite, natural graphite, andmodified graphite. The silicon-based material may be selected from oneor more of elemental silicon, a silicon-oxygen compound, asilicon-carbon composite, and a silicon alloy. The tin-based materialmay be selected from one or more of elemental tin, a tin-oxygencompound, and a tin alloy. The negative electrode current collector maytypically be a structure or a part that can collect current. Thenegative electrode current collector may be a variety of materialssuitable for use as the negative electrode current collector of alithium-ion battery in the art. For example, the negative electrodecurrent collector may include but is not limited to a metal foil, andmore specifically, may include but is not limited to a copper foil andthe like.

In the lithium-ion battery provided by the embodiments of thisdisclosure, the separator may be of various materials suitable forlithium-ion batteries in the field, for example, including but notlimited to one or more of polyethylene, polypropylene, polyvinylidenefluoride, kevlar, polyethylene terephthalate, polytetrafluoroethylene,polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers.

In the lithium-ion battery provided by the embodiments of thisdisclosure, the electrolytic solution may be various electrolyticsolutions suitable for lithium-ion batteries in the art. For example,the electrolytic solution typically includes an electrolyte and asolvent, and the electrolyte may typically include a lithium salt. Morespecifically, the lithium salt may be an inorganic lithium salt and/oran organic lithium salt, and may specifically include but is not limitedto one or more of LiPF₆, LiBF₄, LiN(SO₂F)₂ (LiFSI for short),LiN(CF₃SO₂)₂ (LiTFSI for short), LiClO₄, LiAsF₆, LiB(C₂O₄)₂ (LiBOB forshort), and LiBF₂C₂O₄ (LiDFOB for short). For another example, aconcentration of the electrolyte may be in a range of 0.8 mol/L to 1.5mol/L. The solvent may be various solvents suitable for the electrolyticsolution of a lithium-ion battery in the art, and the solvent of theelectrolytic solution is typically a non-aqueous solvent, preferably, anorganic solvent, and specifically may include but is not limited to oneor more of ethylene carbonate, propylene carbonate, butylene carbonate,pentene carbonate, dimethyl carbonate, diethyl carbonate, dipropylcarbonate, ethyl methyl carbonate, and the like, or halogenatedderivatives thereof.

The following describes embodiments of this disclosure by using specificexamples. Those skilled in the art can easily learn other advantages andeffects of this disclosure through the content disclosed in thisspecification. This disclosure may further be implemented or appliedthrough other different specific embodiments, and various details inthis specification can also be modified or changed based on differentviewpoints and applications without departing from the spirit of thisdisclosure.

It should be noted that processing devices or apparatuses notspecifically noted in the following embodiments are all conventionaldevices or apparatuses in the art.

In addition, it should be understood that the one or more method stepsmentioned in this disclosure do not exclude that there may be othermethod steps before and after the combined steps or that other methodsteps may be inserted between these explicitly mentioned steps, unlessotherwise specified. It should further be understood that thecombination and connection relationship between one or moredevices/apparatuses mentioned in this disclosure do not exclude thatthere may be other devices/apparatuses before and after the combineddevices/apparatuses or that other devices/apparatuses may be insertedbetween the two explicitly mentioned devices/apparatuses, unlessotherwise specified. Moreover, unless otherwise specified, numbers ofthe method steps are merely a tool for identifying the method steps, butare not intended to limit the order of the method steps or to limit theimplementable scope of this disclosure. In the absence of substantialchanges in the technical content, alteration or adjustment of theirrelative relationships shall be also considered as falling within theimplementable scope of this disclosure.

EXAMPLE 1

Preparation of a Positive Electrode Material

Step 1: A substrate precursor was prepared. Nickel sulfate, manganesesulfate, and cobalt sulfate were mixed at a molar ratio of 8:1:1 into anaqueous solution with a concentration of 1 mol/L. The aqueous solutionwas stirred for 6 h at a stirring speed of 1000 rpm, a water bathtemperature of 55° C. and pH of 11, and aged for 12 h at roomtemperature. After filtering and washing, the precursorNi_(0.8)Co_(0.1)Mn_(0.1)(OH)₂ of 9 μm to 11 μm transition metal oxidewas obtained.

Step 2: The substrate precursor Ni_(0.8)Co_(0.1)Mn_(0.1)(OH)₂ obtainedin step 1 and lithium hydroxide were mixed in a high-speed mixer with amolar ratio of the substrate precursor to the lithium hydroxide being1.05, then the mixture was transferred to an oxygen atmosphere furnace(30% oxygen) and sintered there for 10 h at 910° C., accompanied byairflow crushing, to obtain a substrate of the positive electrodematerial with a single crystal structure.

Step 3: The substrate of the positive electrode active material and analumina compound with 0.5 wt % were mixed in the mixer, and then themixture was transferred to the oxygen atmosphere furnace and sinteredthere at 450° C. to form a coating layer of the positive electrodeactive material. Thus, a finished positive electrode material wasobtained.

EXAMPLE 2

It is the same as Example 1 except that in step 2, 0.2 wt % zirconiumoxide was added, and the sintering temperature was set to 900° C.

EXAMPLE 3

It is the same as Example 1 except that in step 2, 0.3 wt % zirconiumoxide was added, and the sintering temperature was set to 900° C.; andthe coating in step 3 was a boron oxide compound, and the amount of thecoating fed was set to 0.2 wt %.

EXAMPLE 4

It is the same as Example 1 except that in step 2, 0.1 wt % zirconiumoxide was added, the sintering temperature was set to 800° C., thesintering time was 9 h, and no airflow crushing was performed; and thecoating in step 3 was aluminum oxide and boron oxide, where the amountof the aluminum oxide coating fed was set to 0.3 wt %, and the amount ofthe boron oxide coating fed was set to 0.2 wt %.

EXAMPLE 5

It is the same as Example 1 except that in step 2, 0.3 wt % niobiumoxide was added, the sintering temperature was set to 800° C., thesintering time was 8.5 h, and no airflow crushing was performed.

EXAMPLE 6

It is the same as Example 1 except that in step 2, 0.2% tungsten oxidewas added, the sintering temperature was set to 800° C., the sinteringtime was 8.5 h, and no airflow crushing was performed; and the coatingin step 3 was 0.3 wt % boron oxide, where the sintering temperature ofthe coating was set to 500° C.

EXAMPLE 7

It is the same as Example 1 except that in step 2, 0.1 wt % zirconiumoxide was added, and the initial sintering temperature was set to 900°C., the sintering time was 7.5 h, no airflow crushing was performed, andthe oxygen concentration was 35%; and the coating in step 3 was aluminumoxide, and the amount of the coating fed was set to 0.2 wt %.

EXAMPLE 8

It is the same as Example 1 except that in step 2, 0.3 wt % titaniumoxide was added, and the sintering temperature was set to 900° C., thesintering time was set to 12 h, and no airflow crushing was performed;and the coating in step 3 was aluminum oxide, and the amount of thecoating fed was set to 0.4 wt %.

COMPARATIVE EXAMPLE 1

It is the same as Example 4 except that in step 1, the aqueous solutionwas stirred for 5 h at a stirring speed of 1500 rpm, a water bathtemperature of 45° C., and pH of 9, and aged 9 h at room temperature;and in step 2, the sintering temperature was set to 920° C., the oxygenconcentration was 20%, no airflow crushing was performed, and the amountof the coating fed was set to 0.1 wt %.

COMPARATIVE EXAMPLE 2

It is the same as Example 4 except that in step 1, the aqueous solutionwas stirred for 5 h at a stirring speed of 500 rpm, a water bathtemperature of 85° C., and pH of 14, and aged 13 h at room temperature;in step 2, 1.2 wt % zinc oxide was added, the sintering temperature wasset to 900° C., the sintering time was 7.5 h, the oxygen concentrationwas 40%, and no airflow crushing was performed; and in step 3, theamount of the coating fed was set to 0.2 wt %.

COMPARATIVE EXAMPLE 3

It is the same as Example 1 except that in step 1, the aqueous solutionwas stirred for 5 h at a stirring speed of 1600 rpm, a water bathtemperature of 45° C., and pH of 9.5, and aged 9 h at room temperature;and in step 2, the sintering temperature was set to 950° C., thesintering time was 11.5 h, and the oxygen concentration was 35%.

COMPARATIVE EXAMPLE 4

It is the same as Example 1 except that in step 1, the aqueous solutionwas stirred for 5 h at a stirring speed of 600 rpm, a water bathtemperature of 80° C., and pH of 13, and aged 13 h at room temperature;in step 2, 1.5 wt % niobium oxide was added, the sintering temperaturewas set to 900° C., the sintering time was 8 h, and the oxygenconcentration was 20%; and in step 3, the coating is magnesium oxide,and the amount of the coating fed was set to 0.2 wt %.

All batteries were prepared according to the following method.

(1) Preparation of a Positive Electrode Plate:

Step 1: A high nickel ternary as a positive electrode material,polyvinylidene fluoride as a binder, and acetylene black as a conductiveagent were mixed in a mass ratio of 98:1:1. N-methylpyrrolidone (NMP)was added. The resulting mixture was stirred by using a vacuum mixeruntil the mixture was stable and uniform, to obtain a positive electrodeslurry. The positive electrode slurry was applied uniformly on a12-pm-thick aluminum foil.

Step 2: The coated electrode plate was dried in an oven at 100° C. to130° C.

Step 3: Cold pressing and cutting were performed to obtain a positiveelectrode plate.

(2) Preparation of a Negative Electrode Plate

Graphite as a negative electrode active material, sodium carboxymethylcellulose as a thickener, styrene butadiene rubber as a binder, andacetylene black as a conductive agent were mixed at a mass ratio of97:1:1:1, deionized water was added, and the mixture was stirred byusing a vacuum mixer to obtain a negative electrode slurry. The negativeelectrode slurry was uniformly applied onto an 8-μm-thick copper foil,the copper foil was dried at room temperature and transferred to an ovenat 120° C. for further drying for 1 h, and then cold pressing andcutting were performed to obtain a negative electrode plate.

(3) Preparation of an Electrolytic Solution

An organic solvent was a mixture containing ethylene carbonate (EC),ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), where a volumeratio of EC, EMC, and DEC was 20:20:60. In an argon atmosphere glove boxwith water content less than 10 ppm, fully dried lithium salt LiPF₆ wasdissolved in the organic solvent to obtain an evenly mixed electrolyticsolution, where concentration of the lithium salt was 1 mol/L.

(4) Preparation of a Separator

A 12-μm-thick polypropylene membrane was used as a separator.

(5) Preparation of a Battery

The positive electrode plate, the separator, and the negative electrodeplate were stacked in order, so that the separator was sandwichedbetween the positive and negative electrode plates for isolation. Then,the stack was wound to obtain a square bare cell which was wrapped withan aluminum plastic film and baked at 80° C. to remove water. Then, thenon-aqueous electrolytic solution was injected, followed by sealing,standing, hot and cold pressing, chemical conversion, clamping, andaging, to obtain a finished battery.

Test Method

(1) Powder Resistivity Test

The powder resistivity test was performed on the positive electrodematerials prepared in the examples and comparative examples. The testmethod is as follows:

A four-probe method was used to test the powder resistivity of thepositive electrode active material under 12 MPa. The test methodincluded: adding 0.4 g of positive electrode active material powder to asample mold (with an inner diameter of 11.28 mm), applying 12 MPapressing force to the powder through a press machine, and reading thepowder resistivity of the positive electrode active material under 12MPa through a resistivity meter after the pressure was stabilized. Thetest results of the examples and comparative examples are shown in Table1.

(2) OD Test Method:

The 35° to 50° interval in the XRD pattern of the tested sample wasslowly (≤2°/min) scanned, and the image was processed with smoothing,filtering, and background removal to obtain I₁₀₁, I₀₁₂ and I₁₀₄, andfurther calculation was performed to obtain OD1 and OD2.

This test method is simple and effective with extremely low cost. Itonly requires targeting at the fixed 2Theta angle interval of thematerial.

(3) MMS Test Method:

The 15° to 70° interval in the XRD pattern of the tested sample wasslowly (≤2°/min) scanned, and the image was processed with smoothing,filtering, and background removal, and the diffraction peak half-highwidths β_(hkl) and diffraction angles θ_(hkl) corresponding to thediffraction peaks of the (003), (101), (012), (104), (105), (107),(018), (110), and (113) crystal planes were calculated, and these valueswere substituted into the formula MMS=(β_(hkl)·cot θ_(hkl))/4 to obtainthe mean microstress (Mean Microstress).

(4) Quantity of Cycles at 60° C. (Fading to 90%):

Cycle Test of the Battery:

1. Adjust the furnace temperature to 45° C., and rest 2 h.

2. CC 1 C to 4.2V, CV 4.2V to 0.05 C.

3. Rest 5 min.

4. DC 1 C to 2.8V.

5. Rest 5 min.

6. Repeat step 2 to step 5 until the capacity fades to 90%.

(5) High-Temperature Storage Volume Swelling Rate at 80° C.:

The battery was fully charged at 1 C to 4.2V and then placed in athermostat at 80° C. for 30 days. A volume swelling rate of the batterywas obtained by measuring an initial volume of the battery and thevolume after standing for 30 days using a drainage method.

Volume swelling rate of the battery (%)=(Volume after standing for 30days/Initial volume−1)×100%

TABLE 1 Mean Powder Particle microstress resistivity No. morphology OD1OD2 MMS (Ω · cm) Example 1 Single crystal 1.77 0.69 0.06 4123 Example 2Single crystal 1.83 0.70 0.04 3986 Example 3 Single crystal 1.83 0.700.03 1258 Example 4 Polycrystalline 1.90 0.73 0.10 1107 Example 5Polycrystalline 1.87 0.72 0.14 3251 Example 6 Polycrystalline 1.87 0.720.15 4286 Example 7 Polycrystalline 1.79 0.71 0.18 2491 Example 8Polycrystalline 1.88 0.74 0.12 2388 Comparative Polycrystalline 1.760.65 0.22 5195 Example 1 Comparative Polycrystalline 1.92 0.81 0.06 4648Example 2 Comparative Single crystal 1.75 0.68 0.08 5276 Example 3Comparative Single crystal 1.91 0.76 0.02 4532 Example 4

TABLE 2 Quantity of High-temperature cycles at 60° C. storage volume No.(fading to 90%) swelling rate at 80° C. Example 1 341 10.2% Example 2488 8.9% Example 3 532 5.4% Example 4 461 9.3% Example 5 363 12.5%Example 6 315 12.9% Example 7 271 9.4% Example 8 392 7.2% ComparativeExample 1 122 45.9% Comparative Example 2 229 30.9% Comparative Example3 132 40.3% Comparative Example 4 282 13.6%

From Table 1 and Table 2, it can be learned that the oxygen defect levelis closely related to the high temperature (60° C.) cycle life and thevolume swelling rate under high temperature storage: as the oxygendefect level decreased (the value of OD1 or OD2 increases), the positiveelectrode material had a more complete crystal structure, so that thecrystal structure was not prone to be damaged during high temperaturecycling, hence a longer high temperature cycle life. In addition, sincethe positive electrode material had a more complete crystal structure,the mean microstress MMS of particles and the residual lithium contenton the surface are both lower, and the gassing problem under hightemperatures storage was also effectively alleviated. In addition,further reducing the powder resistivity of the finished material couldalso increase the high temperature cycle life.

In Comparative Example 1 and Comparative Example 3, the oxygen defectlevels OD1 and OD2 of the high nickel ternary positive electrodematerial were excessively low, which indicates excessive oxygen defectscontent in the material, so the contact interface with the electrolyticsolution was chemically active and prone to side reactions, resulting inexcessive high temperature volume swelling of the battery and moreserious gassing, while deteriorating the cycle performance. The oxygendefect levels OD1 and OD2 of the positive electrode materials inComparative Example 2 and Comparative Example 4 were excessively high,which indicates fewer oxygen defects content in the surface of thepositive electrode material after modification by coating but greatimpact on transmission of lithium ions. The batteries prepared by usingsuch material had excessive impedance, which affected the long-termcycle performance.

In conclusion, this disclosure effectively overcomes variousdisadvantages in the prior art and is highly industrially applicable.

The foregoing embodiments only illustrate the principles and effects ofthis disclosure by using examples, but are not intended to limit thisdisclosure. Any person familiar with this technology can makemodifications or changes to the foregoing embodiments without departingfrom the spirit and scope of this disclosure. Therefore, all equivalentmodifications or changes made by a person of ordinary skill in thetechnical field without departing from the spirit and technical ideasdisclosed in this disclosure shall still fall within the scope of theclaims of this disclosure.

What is claimed is:
 1. A positive electrode material, comprising asubstrate, wherein a general formula of the substrate isLi_(x)Ni_(y)Co_(z)M_(k)Me_(p)O_(r)A_(m), wherein 0.95≤x≤1.05, 0.5≤y≤1,0≤z≤1, 0≤k≤1, 0≤p≤0.1, 1≤r≤5.2, 0≤m≤2, m+r≤2, M is selected from Mnand/or Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V,Ti, Sr, Sb, Y, W, and Nb, and A is selected from one or more of N, F, S,and Cl; and an oxygen defect level of the positive electrode materialsatisfies at least one of condition (1) and condition (2): (1)1.77≤OD1≤1.90, wherein OD1=(I₁₀₁/I₀₁₂)^(0.5), I₁₀₁ represents XRDdiffraction peak intensity of the (101) crystal plane of the positiveelectrode material in an XRD pattern, and I₀₁₂ represents diffractionpeak intensity of the (012) crystal plane of the positive electrodematerial in the XRD pattern; and (2) 0.69≤OD2≤0.74, whereinOD2=(I₁₀₁/I₁₀₄)^(0.5), I₁₀₁ represents the XRD diffraction peakintensity of the (101) crystal plane of the positive electrode materialin the XRD pattern, and I₁₀₄ represents diffraction peak intensity ofthe (104) crystal plane of the positive electrode material in the XRDpattern.
 2. The positive electrode material according to claim 1,wherein the positive electrode material satisfies both the condition (1)and the condition (2).
 3. The positive electrode material according toclaim 1, wherein when the positive electrode material is single-crystalor single-crystal-like particles, OD1 ranges from 1.77 to 1.87; and whenthe positive electrode material is secondary particles, OD1 ranges from1.79 to 1.90.
 4. The positive electrode material according to claim 1,wherein when the positive electrode material is single-crystal orsingle-crystal-like particles, OD2 ranges from 0.69 to 0.72; and whenthe positive electrode material is secondary particles, OD2 ranges from0.70 to 0.74.
 5. The positive electrode material according to claim 1,wherein a Li/Ni mixing ratio of the positive electrode material is 0.1%to 3%, and preferably, the Li/Ni mixing ratio of the positive electrodematerial is 0.5% to 2%.
 6. The positive electrode material according toclaim 1, wherein a mean microstress MMS of the positive electrodematerial ranges from 0.03 to 0.20, wherein MMS=(β_(hkl)·cot θ_(hkl))/4,β_(hkl) represents a half-peak width of a characteristic diffractionpeak (hkl) in the XRD pattern of the positive electrode material, andθ_(hkl) represents a diffraction angle corresponding to thecharacteristic diffraction peak (hkl) in the XRD pattern of the positiveelectrode material; and preferably, when the positive electrode materialis single-crystal or single-crystal-like particles, MMS ranges from 0.03to 0.07; and when the positive electrode material is secondaryparticles, MMS ranges from 0.07 to 0.20.
 7. The positive electrodematerial according to claim 1, wherein the substrate internally containsa doping element, and the doping element is selected from one or more ofMg, Al, Ti, Co, Fe, Cd, Zr, Mo, Zn, B, P, Cu, V, and Ag.
 8. The positiveelectrode material according to claim 1, wherein the positive electrodematerial further comprises a coating layer located on a surface of thesubstrate, the coating layer comprises a coating element, and thecoating element is selected from one or more of Al, Ba, Zn, Ti, W, Y,Si, Sn, and B; and preferably, a content ratio of the coating element inthe positive electrode material is 100 ppm to 3000 ppm, more preferably,200 ppm to 2000 ppm.
 9. The positive electrode material according toclaim 1, wherein powder resistivity ρ of the positive electrode materialunder 12 MPa is 10 Ω·cm to 4500 Ω·cm, and preferably, the powderresistivity ρ is 1000 Ω·cm to 4000 Ω·cm.
 10. The positive electrodematerial according to claim 1, wherein in residual lithium on thesurface of the positive electrode material, Li₂CO₃ content is less than3000 ppm, and LiOH content is less than 5000 ppm; and preferably, theLi₂CO₃ content is less than the LiOH content.
 11. A positive electrodeplate, comprising a positive electrode current collector and a positiveelectrode active material layer, wherein the positive electrode activematerial layer comprises the positive electrode material according toclaim
 1. 12. An electrochemical energy storage apparatus, comprising thepositive electrode material according to claim 1, or the positiveelectrode plate according to claim 11.